Linear programming control of a group of heat pumps

For a new district in the Dutch city Meppel, a hybrid energy concept is developed based on bio-gas co-generation. The generated electricity is used to power domestic heat pumps which supply thermal energy for domestic hot water and space heating demand of households. In this paper, we investigate direct control of the heat pumps by the utility and how the large-scale optimization problem that is created can be reduced significantly. Two different linear programming control methods (global MILP and time scale MILP) are presented. The latter solves large-scale optimization problems in considerably less computational time. For simulation purposes, data of household thermal demand is obtained from prediction models developed for this research. The control methods are compared with a reference control method resembling PI on/off control of each heat pump. The reference control results in a dynamic electricity consumption with many peak loads on the network, which indicates a high level of simultaneous running heat pumps at those times. Both methods of mix integer linear programming (MILP) control of the heat pumps lead to a much improved, almost flat electricity consumption profile. Both optimization control methods are equally able to minimize the maximum peak consumption of electric power by the heat pumps, but the time scale MILP method requires much less computational effort. Future work is dedicated on further development of optimized control of the heat pumps and the central CHP

Upscaling a district heating system based on biogas cogeneration and heat pumps

The energy supply of the Meppel district Nieuwveense landen is based on biogas cogeneration, district heating, and ground source heat pumps. A centrally located combined heat and power engine (CHP) converts biogas from the municipal wastewater treatment facility into electricity for heat pumps and heat for district heating purposes. Development of the urban district is influenced by the current economic and building decline. For the district heating energy concept, a migration strategy for the required infrastructure is required. The migration spans the district’s small-scale starting phase involving 40 houses up to a scale of 176 houses. An optimization model which maximizes profitability is developed which includes data from district heating and cooling demand patterns. With the optimization model, optimal CHP size, boiler size, and operational hours are determined for various scenarios. From the scenario analysis, a migration strategy is developed which starts with a simple system concept supported by boilers to a larger system which includes a CHP. Sustainability in terms of CO2 emission savings of the energy concept is compared with other possible energy concepts

Precise Modeling of the Exoplanet Host Star and CoRoT Main Target HD 52265

This paper presents a detailed and precise study of the characteristics of the Exoplanet Host Star and CoRoT main target HD 52265, as derived from asteroseismic studies. The results are compared with previous estimates, with a comprehensive summary and discussion. The basic method is similar to that previously used by the Toulouse group for solar-type stars. Models are computed with various initial chemical compositions and the computed p-mode frequencies are compared with the observed ones. All models include atomic diffusion and the importance of radiative accelerations is discussed. Several tests are used, including the usual frequency combinations and the fits of the \'echelle diagrams. The possible surface effects are introduced and discussed. Automatic codes are also used to find the best model for this star (SEEK, AMP) and their results are compared with that obtained with the detailed method. We find precise results for the mass, radius and age of this star, as well as its effective temperature and luminosity. We also give an estimate of the initial helium abundance. These results are important for the characterization of the star-planet system.Comment: 9 pages, 6 figures, 7 tables, to be published in Astronomy and Astrophysic

Sizing energy storage in electricity grids containing flexible loads

Flexible loads such as EV chargers and heat pumps have the potential to reduce the amount of energy storage required to handle local power imbalances. However, when sizing energy storage these loads are often neglected. Thereby it is unclear how intelligently controlled flexible loads influence energy storagesizing. Therefore, this paper presents an empirical study into the effect of controlling four different classes of flexible loads on energy storage sizing, under which fall existing technologies such as EV chargers, heat pumps and white-goods. We use a Profile Steering control strategy to minimize the power imbalance over the considered period. Furthermore, we use parameter sweeps to investigate the influences of load availability and load demand on the energy storage sizing, and visualize the energy storage reduction with heat maps.The results show that significant energy storage sizing reductions are possible if flexible loads are considered, including a reduction in capacity of more than 60%. Furthermore, if flexible loads can also supply their buffered power to the local microgrid (such as with V2G applications), the need for energy storage is almost completely removed. We conclude that it is important to consider local flexible devices when sizing storage in order to avoid over-dimensioning

Confirming the Primarily Smooth Structure of the Vega Debris Disk at Millimeter Wavelengths

Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 μm and an angular resolution of 5"; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5"; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10". Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3σ) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained.We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20–100 AU and width ≾50 AU. The interferometric data require that at least half of the 860 μm emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of ≾100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious

Autophagic flux blockage by accumulation of weakly basic tenovins leads to elimination of B-Raf mutant tumour cells that survive vemurafenib

This work was supported by five grants to Sonia Laín: Vetenskapsrådet (VR) 521-2014-3341, Cancerfonden (Swedish Cancer Society) 150393, CAN 2014/702, Association for International Cancer Research (AICR) 130086, Barncancerfonden (Swedish Childhood Cancer Foundation) TJ-2014-0038, Barncancerfonden (Swedish Childhood Cancer Foundation) PR-2014-0038; two grants to Ravi Bhatia: Leukemia and Lymphoma Society (LLS) 6137-14 and NIH R01 CA95684; one grant to David P Lane: Vetenskapsrådet (VR) 538-2013-8807; one grant to Marcus J G W Ladds: Karolinska Institute KID Doctoral Student Funding; one grant to Gergana Popova: Karolinska Institutet KID Doctoral Student Funding; two grants to Nicholas J Westwood: Cancer Research UK C21383 and Cancer Research UK A6950; two grants to Gerald McInerney: Vetenskapsrådet (VR) 621-2014-4718 and Cancerfonden (Swedish Cancer Society) 150393, CAN 2015/751; and four grants to Emmet McCormack: Kreftforeningen 182735, Kreftforeningen 732200, Halse Vest 911884, Halse Vest 911789.Tenovin-6 is the most studied member of a family of small molecules with antitumour activity in vivo. Previously, it has been determined that part of the effects of tenovin-6 associate with its ability to inhibit SirT1 and activate p53. However, tenovin-6 has also been shown to modulate autophagic flux. Here we show that blockage of autophagic flux occurs in a variety of cell lines in response to certain tenovins, that autophagy blockage occurs regardless of the effect of tenovins on SirT1 or p53, and that this blockage is dependent on the aliphatic tertiary amine side chain of these molecules. Additionally, we evaluate the contribution of this tertiary amine to the elimination of proliferating melanoma cells in culture. We also demonstrate that the presence of the tertiary amine is sufficient to lead to death of tumour cells arrested in G1 phase following vemurafenib treatment. We conclude that blockage of autophagic flux by tenovins is necessary to eliminate melanoma cells that survive B-Raf inhibition and achieve total tumour cell kill and that autophagy blockage can be achieved at a lower concentration than by chloroquine. This observation is of great relevance as relapse and resistance are frequently observed in cancer patients treated with B-Raf inhibitors.Publisher PDFPeer reviewe

Event-by-Event Fluctuations of Particle Ratios in Central Pb+Pb Collisions at 20 to 158 AGeV

In the vicinity of the QCD phase transition, critical fluctuations have been predicted to lead to non-statistical fluctuations of particle ratios, depending on the nature of the phase transition. Recent results of the NA49 energy scan program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb collisions at beam energies of 20-30 AGeV. This observation has been interpreted as an indication of a phase transition at low SPS energies. We present first results on event-by-event fluctuations of the kaon to pion and proton to pion ratios at beam energies close to this maximum.Comment: 4 pages, 4 figures, Quark Matter 2004 proceeding

System size dependence of strange particle yields and spectra at sqrt(s)=17.3 GeV

Yields and spectra of strange hadrons (K+, K-, phi, Lambda and Antilambda) as well as of charged pions were measured in near central C+C and Si+Si collisions at 158 AGeV beam energy with the NA49 detector. Together with earlier data for p+p, S+S and Pb+Pb reactions the system size dependence can be studied. Relative strangeness production rises fast and saturates at about 60 participating nucleons; the net hyperon spectra show an increasing shift towards midrapidity for larger colliding nuclei. An interpretation based on the formation of coherent systems of increasing volume is proposed. The transverse mass spectra can be described by a blast wave ansatz. Increasing flow velocity is accompanied by decreasing temperatures for both kinetic and chemical freeze out. The increasing gap between inelastic and elastic decoupling leaves space for rescattering.Comment: 8 pages, 6 figures, Proceedings of the Hot Quarks 2004 worksho

Omega and Antiomega production in central Pb+Pb collisions at 40 and 158 AGeV

Results are presented on Omega production in central Pb+Pb collisions at 40 and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for Omega and Antiomega separately at 158 AGeV. The yields are strongly under-predicted by the string-hadronic UrQMD model and are in better agreement with predictions from a hadron gas models.Comment: 5 papes, 4 figures, 1 table, updated figure 4 and table 1. Final version, including some editorial changes, as published in PR

System-size dependence of strangeness production in nucleus-nucleus collisions at sqrt{s_{NN}}=17.3 GeV

Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as onset of the formation of coherent partonic subsystems of increasing size.Comment: Phys.Rev.Lett in print; version2: changes made according to the request of the referee